Development of Low Cost, High Performance Materials for Microwave Resonator Applications

• Published in: 2002 32nd European Microwave Conference pp. 1 - 3
• Main Authors: Scott, R.I., Thomas, M., Hampson, C.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.09.2002
• Subjects: Base stations; Ceramics; Costs; Dielectric materials; Filtering; Linearity; Microwave filters; Microwave technology; Telephone sets; Temperature
• DOI: 10.1109/EUMA.2002.339262

Microwave dielectric ceramics are utilized in both mobile telecommunication handsets and base station filtering technologies. Other systems such as GPS antennas also require these types of ceramics. There are three major electrical properties that microwave dielectric ceramics must address, ε r (relative permittivity), Q (Quality factor ~1/tanδ) and τ f (temperature co-efficient of resonant frequency). The non linearity coefficient (NLC) is also important, this is a measure of the linearity of τ f as a function of temperature. Ceramic solutions can offer improved performance compared to conventional air cavity filter systems. Dielectrics allow more users for a given bandwidth in addition to being physically smaller, also power handling is improved giving a better signal to noise ratio. However, cost can become a major factor when choosing microwave dielectrics for filter applications. BZT, Ba[Zn ⅓ Ta ⅔ ]O 3 has been the highest performance (ε r ~ 30, Q ~ 55k at 2GHz) temperature stabilized material available to filter engineers. However the high cost (related to the cost of Ta 2 O 5 ) lowers its cost effectiveness for many applications. It has therefore become necessary to formulate a microwave dielectric with similar performance to BZT but at a much reduced cost. Morgan Electro Ceramics have elected to produce a replacement material based on the Ba[(Zn/Co) ⅓ Nb ⅔ ]O 3 system. This paper discusses the role of the latest microwave dielectric under development in current and future filtering technologies. Also discussed is the method of development and specific research issues raised by this requirement, including a recent patent application.